The present invention relates to an isolated phase bus system, and more particularly to a method for fabricating such an isolated phase bus system.
Various isolated phase bus systems have been disclosed heretofore. Exemplary isolated phase bus systems are shown in U.S. Pat. No. 2,972,005, entitled, "Isolated Phase Bus Duct Apparatus", issued to Brealey et al on Feb. 14, 1961, and assigned to the assignee of the present application. Another exemplary isolated phase bus system is shown in U.S. Pat. No. 3,654,378, entitled "Bus Duct Assembly", issued to Rehder on Apr. 4, 1972, and assigned to Canadian General Electric Company, Ltd.
In one typical system, a cylindrical bus conductor is secured to a plurality of spaced-apart relatively fragile insulator assemblies and mounted within a mating hollow cylindrically shaped enclosure which is maintained at ground potential. Each insulator assembly electrically insulates the cylindrical bus conductor from the surrounding enclosure and also provides support for the bus conductor. Typically, an end of the insulator assembly is secured, e.g., welded, to the enclosure at one of a plurality of mounting openings in the enclosure. Generally, the cylindrical bus conductor is respectively provided with mounting and access openings along its length through which mounting hardware, e.g., threaded bolts, can be inserted for securing the bus conductor to an unsecured opposing end of each one of the insulator assemblies. In addition to its mounting openings, the enclosure is also provided with access openings which are useful for servicing and installation purposes. The enclosure access openings are generally disposed in a position in-line with the bus conductor access openings. As will be appreciated more fully later, the enclosure mounting openings should also be disposed in a position in-line with the bus conductor mounting openings.
Although the isolated phase bus systems heretofore discussed are satisfactory for many applications, they do suffer from certain problems, One such problem is that from a manufacturing standpoint, it is very difficult to satisfactorily align the access and mounting openings in the bus conductor structure with the respective access and mounting openings in the enclosure structure. More particularly, the access and mounting openings in the bus conductor and mating enclosure, and the typical bus conductor mounting system associated therewith, impose subtantial constraints upon the assembly of the isolated phase bus system. That is, in the assembly of such a system, after one end of each of the insulator assemblies is secured, e.g., welded, to the enclosure, the appropriate bus conductor openings must be carefully, and properly aligned with the opposing end of each one of the now-secured insulator assemblies. Indeed, if not properly aligned, proper mounting within the enclosure, and securing of the bus conductor to the opposing end of each one of the already secured insulator assemblies, becomes very difficult.
To further appreciate the importance of: (1) the proper alignment of the mounting openings in the bus conductor with the mounting openings in the mating enclosure; and, (2) the proper alignment of the access openings in the bus conductor with the access openings in the mating enclosure, reference will be taken to FIG. 1.
FIG. 1 schematically depicts an isolated phase bus system, generally designated 10, in which a cylindrical bus conductor 12 is disposed in a mating cylindrical enclosure 14 and supported by double insulator assemblies, 16A, 16B, at spaced locations along the length of the bus conductor. The cylindrical bus conductor 12 and the enclosure 14 are of approximately the same length with each of the members 12, 14 respectively comprising a plurality of segments joined together end-to-end to achieve the desired length. At spaced points along the length of the bus conductor 12, the insulator assemblies 16A, 16B are provided. The insulator assemblies 16A, 16B are angularly spaced, e.g., 90.degree. apart, around the longitudinal axis of bus conductor 12 and secured to the conductor as shown more fully in the sectional view of FIG. 2. (Note that a sectional view taken along line 2A--2A of FIG. 1 is substantially identical to the sectional view of FIG. 2). As shown by dashed lines in FIGS. 2, 3, substantial angular and longitudinal alignment is required between: the bus conductor mounting openings 18C and the enclosure mounting openings 18E; and, the bus conductor access opening 20C and the enclosure access opening 20E. Inspection of FIGS. 2, 3 reveals that any misalignment between openings 18C and 18E places severe stresses on the fragile insulator assemblies 16A, 16B. Indeed, such misalignment may render it impossible to properly assemble the isolated phase bus system 10 of FIG. 1.
In view of the importance of the previously mentioned angular and longitudinal alignment of mounting and access openings in the bus conductor and enclosure, fabrication of such isolation phase bus systems involves techniques which require precise control. For example, one technique involves: laying out all the necessary openings on a flat sheet of metal; cutting the appropriate openings; then, rounding out the flat sheet of metal into a cylindrical shape. This method is time consuming and carries a high likelihood of creating serious errors in the transformation from a two dimensional workpiece to a three dimensional workpiece. Other techniques which have been considered include tracing predetermined patterns on already existing cylindrical workpieces. Such techniques are generally awkward and inefficient.
Accordingly, a general object of the present invention is to provide a method for efficiently fabricating an isolated phase bus system of the type which includes a cylindrical bus conductor member insulatingly secured within a mating enclosure.
Another object of the present invention is to provide such a method in which alignment problems associated with bus conductor and enclosure openings are substantially reduced.
Another object of the present invention is to provide such a method which includes automated control means.